The present invention relates to a seat recliner and, in particular, to a powered seat-recliner system having a lightweight plastic transmission housing with high load-carrying capacity.
In a conventional power linear seat-recliner system, a central motor drives a single or pair of actuator cables that, in turn, plug into gear nut(s) that engage threaded shaft(s) in transmission housings on opposite lateral sides of the seat. The threaded shafts, which reciprocate linearly, are secured to a pivoting mechanism that provides seat back reclining adjustment proportional to the linear motion of the threaded shaft.
Typically, transmission housings are cast aluminum, which is relatively expensive and suffers from varying dimensions as the die-cast mold wears. That is, as a mold is repeatedly used to cast aluminum transmission housings, wear on the mold through repeated use eventually skews the dimensions of the die cast parts. Because the transmission housing is a precision part, such wear causes the part to fail to meet required tolerances, often requiring that tolerances be met by adding thrust bearings of varying widths. Further, aluminum is a relatively expensive material from which to make transmission housings.
Notwithstanding the problems associated with mold wear, cast aluminum recliner housings have achieved widespread acceptance due, at least in part, to the ability of the aluminum material and cast housing to withstand the significant forces present during use. The magnitude of these forces, in conjunction with the need to insure that the transmission housing is robust in construction and performance, have dissuaded acceptance of transmission housings formed of alternative materials. However, a need remains for a less expensive and lightweight transmission housing that meets or exceeds the operational capabilities of accepted cast aluminum housings.